Feed controlling method and system

ABSTRACT

A drilling head and drill string is fed, or the feed is restrained, by a hydraulic-fluid-actuated piston. Hydraulic lines supplying and evacuating hydraulic fluid to and from the piston have gauges connected thereto to signal pressure conditions, in psi, at the piston. Scales calibrated in pounds are mounted adjacent to the gauges to signal, per machine and drill string and their characteristics, as well as the characteristics of the material being drilled, a proper correspondence between actual bit weight and an optimum feed pressure of fluid pressure assistance or restraint. A valve controls the hydraulic fluid supply and evacuation, selectively, to effect a holding back of the drill string, when its dead weight less the system&#39;&#39;s internal resistance would produce excessive bit weight, a pulling down of the drill string when its dead weight less the system&#39;&#39;s internal resistance would yield inadequate bit weight or pressure monitoring on a level just to offset the system&#39;&#39;s internal resistance when the drill string weight alone would produce the optimum bit weight (i.e., zero hold-back). The gauges and scale advise the operator of the operational feed status that he might determine the requirements for holding back or pulling down the drill string. Valving at a fluid reservoir insures maintenance of a constant compensating pressure to one side of the piston at all times. This constant pressure, when minimum hold-back pressure is applied, provides a low pressure pull-down force to counteract the system&#39;&#39;s internal resistance so zero hold-back can exist. (The system&#39;&#39;s internal resistance is the sum of various stationary mechanical frictions and the minimum obtainable holdback pressure all acting against the development of a down motion of the drill string.) The compensating pressure also prevents possible cavitation.

United States Patent I Gyongyosi [is] 3,659,655 51 May 2,1972

[54] FEED CONTROLLING METHOD AND SYSTEM [72] Inventor:

[73] Assignee: Ingersoll-Rand Company, New York, NY.

221 Filed: June 2,1970

21 Appl.No.: 42,627

Laszlo Gyongyosl, Clarksburg, W. Va.

Bullock ..173/9 173/152 x 464,182 12/1891 2,940,263 ,6/1960 CudnohufskyFOREIGN PATENTS OR APPLICATIONS 634,421 3/1950 Great Britain ..173/9Primary Examiner-Ernest R. Purser Attorney-Frank s. Troidl, David w.Tibbott and Bernard J.

Murphy [57] ABSTRACT A drilling head and drill string is fed, or thefeed is restrained,

by a hydraulic-fluid-actuated piston. Hydraulic lines supplying andevacuating hydraulic fluid to and from the piston have gauges connectedthereto to signal pressure conditions, in psi, at the piston. Scalescalibrated in pounds are mounted adjacent to the gauges to, signal, permachine and drill string and their characteristics, as well as thecharacteristics of the material being drilled, a proper correspondencebetween actual bit weight and an optimum feed pressure of fluid pressureassistance or restraint. A valve controls the hydraulic fluid supply andevacuation, selectively, to effect a holding back of the drill string,when its dead weight less the system s internal resistance would produceexcessive bit weight, a pulling down of the drill string when its deadweight less the system s internal resistance would yield inadequate bitweight or pressure monitoring on a level just to offset the systemsinternal resistance when the drill string weight alone would produce theoptimum bit weight (i.e., zero hold-back). The gauges and scale advisethe operator of the operational feed status that he might determinethe'requirements for holding back or pulling down the drill string.Vaiving at a fluid reservoir insures main- -tenance of a constantcompensating pressure to one side of the piston at all times. Thisconstant pressure, when minimum hold-back pressure is applied, providesa low pressure pulldown force to counteract the system's internalresistance so zero hold-back can exist. (The systems internal resistanceis the sum of various stationary mechanical frictions and the minimumobtainable hold-back pressure all acting against the development of adown motion of the drill string.) The compensating pressure alsoprevents possible cavitation.

14 Claims, 1 Drawing Figure FEED CONTROLLING METHOD AND SYSTEM it isalready known in the art to provide drilling machine feed controllingsystems which are operative in response to an enabling supply ofpressured fluid, such systems being powered either by a fluid-actuatedpiston, or the like, but the known systems do not provide any visualindication of the fluid pressure subsisting in the system. Accordingly,the system operator has little opportunity for determining whether ornot the feed pressure being applied is excessive or inadequate for theweight of the drill string in service. Also, in that the known systemsdo not provide a visual indication of the pressures subsisting in thefeed system, the operator has no means for determining when to reduce orcut off the feed pressure and when, if he has such facility at hisdisposal, hydraulically to hold back the feed of the drill string.

It is an object of this invention, therefore, to teach a feedcontrolling system which is operative in response to an enabling supplyof pressured fluid having means indicative of fluid pressures subsistingin the system.

It is another object of this invention to teach a feed controllingsystem, of the type noted, with means for providing pressured fluid to,and evacuating pressured fluidfrom, the system, including meansautomatically operative for maintaining not less than a prescribed levelof the supply of pressured fluid in the system.

It is another object of the invention to teach a feed controllingsystem, of the type noted, with scale means, mounted adjacent to thepressure indicating means, having indicia inscribed thereon to establisha correspondence between said indicia and said pressure indication.

This invention has as another object the teaching of a method of feedcontrol, for drilling machines having drill rod depending from adrilling head which is supported by, and movable relative to, a drilltower, and given fluid-actuable motor means, having opposedfluid-reacting surfaces, coupled to the drilling head for effectingmovement thereof, comprising supplying a pressured fluid for actuationof said motor means; supplying a reservoir for receipt of fluid fromsaid motor means; directing the supplied, pressured fluid, selectively,to one of said surfaces, and communicating another of said surfaces withthe reservoir; and measuring the pressures of supplied fluid subsistingat said motor means.

As yet another object, this invention teaches the method just notedwherein the provisioning of pressured fluid includes always maintainingnot less than a prescribed level of supply of pressured fluid to themotor means.

A feature of this invention comprises the disposition of pressure gaugesin the hydraulic lines which supply or evacuate hydraulic fluid to and afeed-actuating piston, the gauges being provisioned to signal pressureconditions at the piston.

Another feature of this invention comprises the provisioning of scalescalibrated in pounds, the scales being mounted adjacent to the pressuregauges to signal, per machine and drill string and theircharacteristics, as well as the characteristics of the material to bedrilled, a proper correspondence between an actual bit weight and anoptimum feed pressure of fluid assistance or restraint therefor.Accordingly, by noting a disparity between the psi rating on the gaugingand the optimum feed in pounds as calibrated in the scales, an operatoris then guided in deciding upon the provisioning of more or lesshydraulic feed pressure to one side of the piston to vary the feedassistance or to the other side of the piston to vary the feedrestraint).

Another feature of the invention comprises the provisioning of valvingat a fluid reservoir which insures the maintenance of a prescribed levelof compensating pressure at one side of the piston, at all times, toovercome the built-in internal resistances of the system which aresignificant enough that they could upset the feed motion in downwarddirection without this compensating pressure acting on the lower side ofthe piston when minimum restraining pressure is applied on the upperside of the piston. It also prevents cavitation.

Further objects and features of this invention will become more apparentby reference to the following description taken in conjunction with theaccompanying figure which is a pictorial sketch, in a side elevationalview, of a drilling machine which shows the tower with one of itsmounting feet, the drilling head with a drill string dependingtherefrom, and the feed chains secured to the drilling head and towerand showing an actuating hydraulic piston operatively associated with aschematic diagram of an embodiment of the novel feed controlling system.

As shown in the figure a drill tower 10 comprises a frame 12 forsupporting a drilling head 14 for sliding movement along verticalmembers of the frame. The frame 12 is supported upon the surface of theground by a plurality of members 16 (only one being shown) having feet18 at ends thereof. A drill string 20 depends from the drilling head 14and the foremost drill rod thereon carries a drilling bit 22 for workingpenetration of the material being drilled.

The drilling head 14 carries anchors 24 at either sides thereof (onlyone being shown), and chains 26 are affixed to either ends of theanchors for effecting movement of the drilling head 14 relative to thetower 10. An idler pulley 28 is mounted to the drill tower 10 near thetop thereof, and a second idler pulley 28 is mounted near the bottom ofthe drill tower, and the feed chains 26 are arranged about thesepulleys. Further the feed chains 26 are arranged about a pair of movableidler pulleys 30, and thereafter the terminal end of each chain 26 isfixed to the drill tower at points 32 and 34.

Idler pulleys 30 are carried rotatably in a sheave block 36 to which isfixed an arm or piston rod 38 which extends from a piston 40 disposedwithin a fluid chamber or cylinder 42. Cylinder 42 is pivotally fixed,at one end thereof, at point 44 to the drill tower. Cylinder 42 has twofluid ports 46 and 48'for admitting hydraulic fluid to the oppositesides of piston 40. First and second fluid lines 50 and 52 arethroughconnected with ports 48 and 46, respectively, for supplying orevacuating hydraulic fluid to and from cylinder 42. Line 50 has firstand second terminal sections 54 and 56. So also, the second fluid line52 has a given terminal section 58 and another terminal section 60.

Terminal section 54 provides a fluid connection between port 48 and aselector valve 62, and terminal section 56 provides a fluid connectionbetween valve 62 and a slow feed hydraulicpump 64. The given terminalsection 58 provides a fluid connection between port 46 and valve 62,whereas terminal section 60 provides a fluid connection between valve 62and a pressure reducing valve 66. The slow" feed hydraulic pump 64 issupplied, by means of a line 68, from a fluid supply tank or reservoir70. Pressure reducing valve 66 has a line 72 connected thereto whichterminates in a reservoir 74. Pressure reducing valve 66 also hasanother line 76 connected thereto and extending to a terminal junctionof lines 78.

Junction 78 interconnects a pair of hydraulic lines 80 and 82 which areprovided to supply enabling hydraulic fluid to a motor 84 which is usedfor ancillary equipment of the drilling machine. By way of example only,in this embodiment, motor 84 comprises a rotation motor for rotating thedrill string. Accordingly, line 80, in cooperation with line 82, andanother line 86, are coupled to rotation motor 84 through a rotationdirectional valve 88 to supply enabling hydraulic fluid from a rotationpump 90 to cause rotation of the motor in either the one or thealternate direction. Rotation pump 90 is supplied hydraulic fluid from areservoir 92 by way of a hydraulic line 94. When'valve 88 is in theposition illustrated rotation motor 84 revolves in a given direction.When directional valve 88 is displaced one position the hydraulic fluidis cut off from the rotation motor 84 and rotation of the drill stringis halted. When the directional valve 88 is displaced a further positionrotation motor 84 is turned in the alternate direction to (cause areverse rotation of the drill string).

Lines 82 and 80, through junction 78, are through-connected with line 76to provide the novel feed controlling system with a safety supply ofhydraulic fluid-to maintain the feed controlling system at not less thana given level of fluid pressure. More of this feature will be explainedsubsequently.

It will be noted that terminal sections 54 and 58 have pressure gaugesthroughconnected therewith. Pressure gauge 96, which is connected withterminal section 54, is identified as the hold-back gauge. The gauge 98coupled to terminal section 58 is identified as the pull-down gauge.Gauges 96 and 98 are provided to signal the pressure conditionsobtaining in cylinder 42, at opposite sides of the piston 40, so thatthe operator may determine visually the amount of fluid pressure beingsupplied through line 54 to hold back the drilling head, or the amountof fluid pressure being supplied through line 58 to pull down thedrilling head 14, respectively.

Selector valve 62 is provisioned to effect a pulling down of thedrilling 14 head and drill string 16, a holding back of the drillinghead and string, depending upon the weight, the actual weight of thedrill string together with the weight of the drilling head itself, or toeffect neither a pulling down nor a holding back. As illustrated thesystem is arranged for effecting a pulling down of the drilling head 14and string 16 because terminal section 56 is throughconnected, thoughselector valve 62, with terminal section 58. Accordingly, the slow feedpump 64 supplies a pressured volume of hydraulic fluid to the undersideof piston 40 to move the piston upward. So also, terminal section 54 isconnected, through valve 62, with terminal section 60 and from there,through pressure reducing valve 66, evacuates hydraulic fluid from theupper side of piston40 into reservoir 74. Therefore, the upper side ofpiston 40 has hydraulic, fluid evacuated therefrom, and the underside ofpiston 40 has pressured hydraulic fluid applied thereto to translatepiston rod 38 and sheave block 36 upwardly which in turn causes anchors24 and drilling head 14 to be moved downwardly in, and relative to, thedrill tower 10. The drill string 20 depending from the drilling head isforceably fed, i.e., pulled down, into the material to be drilled.

Pressure reducing valve 66 is preset for a predetermined pressure.Should the pressure of hydraulic fluid in cylinder 42 at the upper sideof piston 40 (due to the evacuation of fluid therefrom) fall below thepreset pressure of valve 66, this valve automatically operates tothroughconnect lines 76 with terminal section 60. This, in turn, insuresthat the upper side of piston 40 will not fall below the notedprescribed and preset pressure level of valve 66. Make up or safetyhydraulic fluid, as required, will be supplied to the upper side ofpiston 40, from rotation pump 90 through line 82 (or line 80, dependingupon the mode of rotation of motor 84).

The optimum feed pressure required for a particular drilling machine ina particular drilling operation, of course, is determined by the weightof the drilling head, such as drilling head 14, the weight of the drillstring, such as'drill string 20, and the relative unyielding nature ofthe material being drilled. Other factors, of course, to a lesserdegree, will enter into a determination of the feed pressure required inany given operation. That is, also to be considered are frictionallosses in motion, the efficiency or configuration of the bit, and so on.However, more significantly we are concerned with the actual totalweight of the drill string, drilling head, and bit. Accordingly, theinvention teaches means for calibrating the novel feed controllingsystem for the particular machine and the operational conditions inwhich it is deployed. Scales 100 and 102, hold-back" and pull-down"scales, are arranged about gauges 96 and 98. They are provided withcalibrated inscriptions or indicia representative of incremental weightsin pounds.

For a particular drilling machine the drilling head will have a known,given weight. Let us say for purposes of illustration that thedrillinghead, without a drill string, weighs 2,000 lbs. Now then, the operatorwill put the selector valve 62 in the hold back position, i.e., theposition in which terminal sections56 and 54, and 58 and 60,respectively, are throughconnected. He will watch the pressure gauge 96until it reaches that pressure indication at which the fluid pressure isreduced to the level where the drilling head 14 starts to slidedownwardly. In drilling, the drilling head moves down, so weighing isdone in the same direction. Whatever is the pressure indication, in psion gauge 96, at that point the operator observes that inscription on thescale 100 at that point (ad- 5 jacent to the gauge indication) is 2,000lbs. of weight. Next the operator can attach a drill rod and bit whichtogether, let us say, weight 1,000 lbs. Again, the operator will put theselector valve 62 in the hold back position while the bit is off theground (to supply pressured fluid to the upper side of piston 40) untilthe fluid pressure and volume is so reduced that the drilling head,drill rod and bit just begin to move down (pressure and weight isequalized). Again, the scale 100 indication, adjacent to the pressurereading shown with this condition, reads 3,000 lbs. in like manner theoperator can determine, each time he adds a drill rod of known orunknown weight, the total weight hanging on the feed chain by observingthe holdback scale for its corresponding inscriptions at the thresholdof the down motion of the drill string.

In deep drilling operations, the operator will find that there is aweight of extended drill string which requires no hydraulic assistanceto cause the drill to penetrate the material. So, the operator willneither hold back nor pull down the drilling head 14 and string 20. Inthis case he will put valve 62 in the holdback position and adjustpressure on gauge 96 until it corresponds with a minimum lbs. reading onscale 100. A full range hold-back, starting from 0 lbs, is not possible.This is due to the provisioning of a prescribed constant pressurecondition in line 60 and at the upper side of piston 40, as noted in thetext earlier. The constant pressure condition is provisioned by a presetpressure reducing valve 66, a pressure supply line 76 and an excesspressure relieving line 72. The combined function of these components isto maintain the constant pres sure condition in line 60 at all times.

It must be understood, however, that components 66, 76, and 72 can beeliminated from the system without departing from the spirit of theinvention if anywhere in the instant hydraulic system, or in ancillarysystems, suitable constant pressure condition source can be found, orcan be created, to which line 60 can be connected. Such sources could bethe inlet portion of a supercharged pump, any pressurized return line,and the like.

Taking an arbitrary example, where the weight of the drill string 20together with the drilling head 14 and bit 22 is 4,000 lbs., and thenature of the material being drilled is such that a proper bit weightfeed is 2,000 lbs. the operator must put selector valve 62 in thehold-back" position until the gauge 96 registers a pressure which is incorrespondence with an inscription signifying 2,000 lbs. on scale 100.Taking another example, if the weight of the drill string 20 togetherwith the drilling head 14 and the bit weight 22 totals 4,000 lbs. butthe nature of the material being drilled is such that a feed or anapparent bit weight of 30,000 lbs. must be applied, properly topenetrate the material, then the operator must put the selector valve 62in the pull down position until gauge 98 reads a pressure correspondingto an inscription on scale 102 of 26,000 lbs.

An adjustable pressure relief valve 104 is coupled to section 56' by wayof a line 106; valve 104 opens on reservoir 92. Valve 104 is adjustableto limit the pressure supplied to piston 40. Accordingly, where thehold-back pressure for a drill string of 4,000 lbs. requires a pressureof 2,000 lbs. on the upper side of piston 40, the adjustability ofpressure relief valve 104 is used to limit the-fluid pressure (as readon gauge 96) so exactly 2,000 lbs. is registered on scale 100. The valve104 is reset, for the optimum pull-down or hold-back feed pressure, eachtime a drill rod is added to drill string 20.

Pump 64 is identified as a slow feed" pump. It cooperates with a pumpsuch as that of rotation pump to feed the drill string 20 while pump 90is causing rotation thereof. However, any drilling machine requires afast feed and retraction of the drill string, quickly to facilitateremoval or addition of drill rods to the drill string. The volume andpressure of fluid provided through pump 64 is adequate and proper fordrilling feed. However, for rod handling, it is more efficient to have apump which can quickly raise and lower the drilling head 14 for thisdrill rod handling, and such a pump is provided in "fast feed pump 108.

Pump 108 is supplied by a reservoir supply 70' through a selector valve62' to opposite sides of piston 40 by way of lines 110 and 112. Beforevalve 62' is put in an enabling position it is, of course, necessarythat valves 88 and 62 be put in their blocked or neutral,non-communicating positions. These valves are shown independentlyoperative only for simplification. However, it is of course quitefeasible to couple or gang the valves 62, 62' and 88 together so that itwould be impossible for valve 62 to be put in either operative positionunless valve 62 where in the blocked position-and the same would holdtrue for valve 88. This is a matter of engineering choice and will beobvious to those skilled in the art.

While I have described my invention in connection with a specificembodiment thereof it is to be clearly understood that this is done onlyby way of example and not as a limitation to the scope of my inventionas set forth in the objects thereof and in the accompanying claims.

I claim:

1. A feed controlling system, for drilling machineshaving drill roddepending from a drilling head which is supported by, and movablerelative to, a drill tower, and given motor means, having opposedfluid-reacting surfaces, coupled to the drilling head for effectingmovement thereof comprising:

at least a first fluid supply and pump means for supplying pressuredfluid to said motor means;

a fluid reservoir; and

means for selectively communicating said fluid supply and pump means andsaid reservoir, respectively, with said opposed surfaces tofluid-pressure one of said surfaces and to evacuate pressured fluid fromanother of said surfaces; wherein said latter means includes means forindicating the level of fluid pressure subsisting on at least one ofsaid surfaces; and

graduated scale means, mounted in adjacency to said pressure indicatingmeans, having weight indicia thereon in graduations to signal, incooperation with said indicating means, an optimum feed condition forthe system. Y 2. A feed controlling system, according to claim 1,further including:

means throughconnected with said reservoir automatically operativealways to maintain not less than a prescribed level of supply ofpressured-fluid to said motor means.

3. A feed controlling system, according to claim 2, wherein:

said communicating means including adjustable valve means forselectively controlling the communication of said fluid supply and pumpmeans with said surfaces.

4. A feed controlling system, according to claim I, further including:

means throughconnecting with said reservoir automatically operativealways to maintain not less than a prescribed level of fluid pressure tosaid motor means.

5. A feed controlling system, according to claim 4, wherein:

said pressured fluid maintaining means includes valving meansautomatically responsive to a given fluid pressure level to haltevacuation of fluid from said motor means.

6. A feed controlling system, according to claim 5, wherein:

said pressured fluid maintaining means further includes a second fluidsupply and pump means, for supplying pressured fluid to ancillary motormeans; and

said valving means includes means for through-connecting said secondfluid supply and pump means with said given motor means.

7. A feed controlling system, according to claim 4, wherein:

said fluid communicating means includes a first conduit means, forconducting pressure fluid therethrough, having first and second terminalsections, said first terminal section thereof opening on one of saidsurfaces, and said second terminal section thereof opening on said firstfluid supply and pump means;

a second conduit means, for conducting pressured fluid therethrough,having both a given and an other terminal section, said given terminalsection thereof opening on the other of said surfaces, and the otherterminal section thereof opening on said reservoir; and

valve means interposed between said first and second sections and alsobetween said given and other terminal sections for accommodating fluidcommunication therebetween,

respectively,

for interrupting fluid communication therebetween, and

for throughcommunicating said second terminal section with said giventerminal section and said first terminal section with said othertenninal section, respectively.

8. A feed controlling system, according to claim 7, wherein:

said valve means is selectively operative.

9. A feed controlling system, according to claim 7, wherein:

said indicating means comprise at least one fluid-pressure gauge inoperative fluid-communication with at least one of said conduit means.

10. A feed controlling system, according to claim 1,

wherein: I

said communicating means include adjustable valve means for selectivelycontrolling the communication of said fluid supply and pump means withsaid surfaces.

11. A method of feed control, for drilling machines having drill roddepending from a drilling head which is supported by, and movablerelative to, a drill tower, and a given fluid-actuable motor means,having opposed fluid-reacting surfaces, coupled to the drilling head foreffecting movement thereof, comprising the steps of:

supplying a pressured fluid for actuation of said motor means;

supplying a reservoir for receipt of fluid from said motor means;

directing the supplied, pressured fluid, selectively, to one of saidsurfaces, and communicating another of said surfaces with the suppliedreservoir;

measuring the pressures of supplied fluid subsisting at said motormeans;

noting a correlation of the measured fluid pressures at said motormeans, which efiect perceptible movements of said drilling head and saiddrill rod, with the actual weights of said drilling head and drill rodof varying lengths; and

setting out weight-representative indicia, ona scale, to be able tocorrelate such movement-effective measured fluid pressures, per drillinghead and drill rod weights, to said scale for reference purposes ineffecting optimum feed per actual weights.

12. A method of feed control for drilling machines, according to claim11, wherein:

said fluid supplying step includes the step of always maintaining notless than a prescribed level of supply of pressured fluid to said motormeans.

13. A method of feed control for drilling machines, according to claim11, further including the step of regulating the pressure of fluidsupplied to said one surface, to limit the pressure to a valuecorrelated to the actual weight of said drilling head and drill rod of agiven length, when such actual weight alone will produce an optimumfeed, to increase the pressure to a value which will produce an optimumfeed when such actual weight is insufiicient to do so, and to reduce thepressure to a value which will produce an optimum feed when such actualweight is too excessive to do so.

14. A method of feed control for drilling machines, according to claim13, wherein:

said pressures-measuring step comprises supplying a visual indication ofpressure measurements; and further includes the step of juxtapositioningsaid scale with said visual indications so as to be able to determinethe amount of pressure regulation eflected and to be effected, for saiddrilling head and drill rods of varying lengths, to achieve said optimumfeed.

# i i i i

1. A feed controlling system, for drilling machines having drill rod depending from a drilling head which is supported by, and movable relative to, a drill tower, and given motor means, having opposed fluid-reacting surfaces, coupled to the drilling head for effecting movement thereof comprising: at least a first fluid supply and pump means for supplying pressured fluid to said motor means; a fluid reservoir; and means for selectively communicating said fluid supply and pump means and said reservoir, respectively, with said opposed surfaces to fluid-pressure one of said surfaces and to evacuate pressured fluid from another of said surfaces; wherein said latter means includes means for indicating the level of fluid pressure subsisting on at least one of said surfaces; and graduated scale means, mounted in adjacency to said pressure indicating means, having weight indicia thereon in graduations to signal, in cooperation with said indicating means, an optimum feed condition for the system.
 2. A feed controlling system, according to claim 1, further including: means throughconnected with said reservoir automatically operative always to maintain not less than a prescribed level of supply of pressured-fluid to said motor means.
 3. A feed controlling system, according to claim 2, wherein: said communicating means including adjustable valve means for selectively controlling the communication of said fluid supply and pump means with said surfaces.
 4. A feed controlling system, according to claim 1, further including: means throughconnecting with said reservoir automatically operative always to maintain not less than a prescribed level of fluid pressure to said motor means.
 5. A feed controlling system, according to claim 4, wherein: said pressured fluid maintaining means includes valving means automatically responsive to a given fluid pressure level to halt evacuation of fluid from said motor means.
 6. A feed controlling system, according to claim 5, wherein: said pressured fluid maintaining means further includes a second fluid supply and pump means, for supplying pressured fluid to ancillary motor means; and said valving means includes means for through-connecting said second fluid supply and pump means with said given motor means.
 7. A feed controlling system, according to claim 4, wherein: said fluid communicating means includes a first conduit means, for conducting pressure fluid therethrough, having first and second terminal sections, said first terminal section thereof opening on one of said surfaces, and said second terminal section thereof opening on said first fluid supply and pump means; a second conduit means, for conducting pressured fluid therethrough, having both a given and an other terminal sectiOn, said given terminal section thereof opening on the other of said surfaces, and the other terminal section thereof opening on said reservoir; and valve means interposed between said first and second sections and also between said given and other terminal sections for accommodating fluid communication therebetween, respectively, for interrupting fluid communication therebetween, and for throughcommunicating said second terminal section with said given terminal section and said first terminal section with said other terminal section, respectively.
 8. A feed controlling system, according to claim 7, wherein: said valve means is selectively operative.
 9. A feed controlling system, according to claim 7, wherein: said indicating means comprise at least one fluid-pressure gauge in operative fluid-communication with at least one of said conduit means.
 10. A feed controlling system, according to claim 1, wherein: said communicating means include adjustable valve means for selectively controlling the communication of said fluid supply and pump means with said surfaces.
 11. A method of feed control, for drilling machines having drill rod depending from a drilling head which is supported by, and movable relative to, a drill tower, and a given fluid-actuable motor means, having opposed fluid-reacting surfaces, coupled to the drilling head for effecting movement thereof, comprising the steps of: supplying a pressured fluid for actuation of said motor means; supplying a reservoir for receipt of fluid from said motor means; directing the supplied, pressured fluid, selectively, to one of said surfaces, and communicating another of said surfaces with the supplied reservoir; measuring the pressures of supplied fluid subsisting at said motor means; noting a correlation of the measured fluid pressures at said motor means, which effect perceptible movements of said drilling head and said drill rod, with the actual weights of said drilling head and drill rod of varying lengths; and setting out weight-representative indicia, on a scale, to be able to correlate such movement-effective measured fluid pressures, per drilling head and drill rod weights, to said scale for reference purposes in effecting optimum feed per actual weights.
 12. A method of feed control for drilling machines, according to claim 11, wherein: said fluid supplying step includes the step of always maintaining not less than a prescribed level of supply of pressured fluid to said motor means.
 13. A method of feed control for drilling machines, according to claim 11, further including the step of regulating the pressure of fluid supplied to said one surface, to limit the pressure to a value correlated to the actual weight of said drilling head and drill rod of a given length, when such actual weight alone will produce an optimum feed, to increase the pressure to a value which will produce an optimum feed when such actual weight is insufficient to do so, and to reduce the pressure to a value which will produce an optimum feed when such actual weight is too excessive to do so.
 14. A method of feed control for drilling machines, according to claim 13, wherein: said pressures-measuring step comprises supplying a visual indication of pressure measurements; and further includes the step of juxtapositioning said scale with said visual indications so as to be able to determine the amount of pressure regulation effected and to be effected, for said drilling head and drill rods of varying lengths, to achieve said optimum feed. 